1)
People are not allowed to go further than the small red bouys
2)
When a vessel approaches; the Beachwatch is whistling to warn
3)
Pilots of the vessels are requested to pass slow ahead; especially the outgoing ones, because the incoming-like this one- are already on slow ahead for embarking the riverpilot..
4)
Common sense...
Hope this helped a little...
kind regards
Geert
Zappa